How the water gets up the mountain: Climate change in Yosemite Valley

פורסם: 9 במאי 2012, 7:10 על ידי: Sustainability Org   [ עודכן 9 במאי 2012, 7:11 ]

04/06/2012 // 

Written by Michael Lanza, Northwest Editor of Backpacker Magazine and creator of The Big Outside.

© 2012 Michael Lanza

Michael Lanza is the Northwest Editor of Backpacker Magazine and the creator of, a website for telling stories and sharing images of America’s best outdoor adventures. His book, Before They’re Gone: A Family’s Year-Long Quest to Explore America’s Most Endangered National Parks, traces his journey to show his kids the iconic national parks that could be altered forever by climate change.

Michael wrote an account for us about a trip with his children to America’s busiest national park, Yosemite. Here is what they learned.

© 2012 Michael Lanza

On a trail more than a thousand feet above Yosemite Valley – a height at which the forest far below more closely resembles a supermarket display of broccoli crowns than tall pine trees – we rounded a bend to the sudden sight of Upper Yosemite Falls, a column of water falling through more than a quarter mile of air.

I asked the three young hikers with me – my seven-year-old daughter Alex, nine-year-old son Nate, and twelve-year-old nephew Marco – “What do you think of that?” But they only stared, saying nothing.

© 2012 Michael Lanza

It’s easy to be hypnotized by the complex liquid topography of Upper Yosemite Falls. A broad curtain of watery tracer bullets arcing downward, it free-falls a sheer 1,430 feet off the rim of a granite cliff – ranking it among the world’s twenty tallest. After slamming into the massive boulders at the waterfall’s base in what is arguably nature’s finest demonstration of an unstoppable force meeting an immovable object, Yosemite Creek drops another 675 feet through cascades before plunging over 320-foot-tall Lower Yosemite Falls. Those three stages give Yosemite Falls a cumulative height of 2,425 feet, sixth highest in the world.

Finally, Alex broke the stunned silence. Her brow knitted in concentration, she asked me, “How does the water go up the mountain?”

I thought: What a great question. To her, Upper Yosemite Falls appears to materialize inexplicably from the top of this 1,400-foot cliff. So I explained that beyond sight up there, a lot of melting snow fills that creek with water.

© 2012 Michael Lanza

On that June day, we hiked nearly 3,000 feet and four miles uphill to the brink of the waterfall and back down, the first of two day hikes we made to Yosemite Valley waterfalls on that trip. Yosemite was the second of eleven wilderness adventures I took with my wife and kids in a year’s time, backpacking, sea kayaking, cross-country skiing, canoeing, and rock climbing in national parks. The parks each face very different threats from warming temperatures because of the complex interactions of climate and local environment — threats different and yet all ominous.

The snow that turns into a waterfall

In Yosemite and throughout the High Sierra, historically one of the snowiest mountain ranges in the world, one certain outcome of a warmer climate will be less snow. In the Sierra, as across the West, snow already melts away and streams reach peak runoff two to four weeks earlier than a half century ago. As this trend continues, precipitation in autumn, winter, and spring will increasingly fall as rain rather than snow, steadily diminishing the mountain snowpack that delivers life-giving waters to a region that receives little summer rainfall.

© 2012 Michael Lanza

By the time my kids are adults, Yosemite Falls and every other waterfall in the park will reach peak runoff weeks or months earlier in the year — in mid- or early spring instead of late spring. This poses a much larger disaster than simply disappointing hikers who want to see waterfalls roaring at the same time that wildflowers are blooming in June and July. The profound effects of water filling streams in spring rather than in summer, when plants and animals most need it, will reverberate throughout ecosystems across the western United States, the region that’s home to many of our big wilderness parks.

“It’s a really frightening thing,” Mike Dettinger, a research hydrologist with the U.S. Geological Survey in California, told me. “Within about twenty years, the Sierra Nevada and Yosemite will be really quite a different place.”

What about the rest of the country?

In the Southwest, the region that is home to our greatest concentration of national parks, the Grand Canyon and other parks face another variation of the impacts from rising temperatures: broiling heat. The Southwest will likely see longer, hotter, more frequent heat waves and longer droughts.

© 2012 Michael Lanza

Even now the Grand Canyon, a confounding labyrinth 277 miles long and more than a mile deep, scored by about three hundred twisting side canyons, receives only about eight inches of rain a year at the canyon bottom – the same as the Gobi Desert. Summer highs routinely top 90 and 100 degrees Fahrenheit. The canyon’s estimated six hundred springs and seeps cover just one-hundredth of 1 percent of the park’s area – but support 100 to 500 times more species than the surrounding desert. If many of them dry up, as researchers fear, many plants and animals would not survive – not to mention that backpacking in the Grand Canyon would become exponentially harder because of the added demands of carrying water for greater distances between sources.

Across the continent, most of Florida’s Everglades, one of Earth’s greatest sanctuaries of biological diversity, could disappear beneath the ocean if sea level rises by two feet. A June 2010 Park Service paper forecasted that a mere 15-inch rise in sea level will erase half of salt marshes, 60 percent of estuarine beaches, and most tidal flats in Gulf Coast areas like the Ten Thousand Islands. But many researchers now project the ocean rising by three to six feet in this century. A Park Service study two years earlier warned of the potential for “catastrophic inundation of South Florida.” At risk are the third-largest coral reef system in the world and the habitats for myriad species, including sixteen types of wading birds, almost 300 kinds of fish, and 36 vertebrates and 26 plant species listed as endangered, threatened, or under consideration for listing.

My seven-year-old daughter had asked me in Yosemite how water gets up the mountain. Someday soon, we may find ourselves struggling with questions just as profound about how our national parks will survive climate change.